There are many situations in the food processing industry wherein food, which may be raw or cooked, is machine-formed into a molded food product. For example, meat, fish, poultry (or various combinations of such foods) that is ground, flaked, chopped (or otherwise processed to place it in a plastic state) is often compressed within a machine to form specific molded portions such as patties, balls or loaves. Generally the machines for forming these molded food products include a mold having one or more cavities of a shape corresponding to the desired shape of the molded product. The food being processed, e.g., ground meat, is delivered to the mold cavities from a hopper or bin and is compressed by a plunger or ram which presses the food into the mold cavities. Since the pressure exerted by the ram not only causes the food particles to adhere to one another, but also determines the density (weight per unit volume) of the molded product, it can be recognized that both the overall consistency of the molded product and the weight of the molded product are related to the volume of the mold cavities and the forming pressure. Specifically, in conventional food forming machines, the mold cavities are dimensioned such that the molded product will be of a desired size and shape with the pressure exerted by the ram being established to provide a molded product of the desired consistency.
Although establishing the volume of the mold cavity and the forming pressure basically determines the density of the molded product (and hence determines the weight of each molded product that is produced), it is generally true that a range of pressures will provide a molded product of satisfactory consistency. Thus, with respect to most conventional food forming machines, a manually operable adjustment mechanism is provided for adjusting the forming pressure so as to control the consistency of the formed product and also permit a certain degree of control over the density (or weight) of the molded product.
Rather precise control of the density and weight of the molded is relatively important to many food processors since oftentimes the molded food product is not sold on the basis of the individual weight of each molded product, but is sold on the basis of a minimum guaranteed weight. In such a situation, if a forming machine produces molded food products below the minimum weight limit, the product cannot normally be sold but often must be reprocessed at considerable expense to the food processor. On the other hand, if the forming machine produces molded food products of a weight that exceeds the minimum weight, the product may be acceptable to the customer, but the cost of the excess food utilized to form the molded food product must be borne by the food processor. When overweight products are produced, operating costs are increased regardless of whether the food processor bears this loss or reprocesses the product.
The manual pressure adjustment mechanism of conventional food forming machines has not provided a satisfactory solution of the problem of maintaining the weight of molded food products substantially constant. First, the density of the food being formed can change rather substantially over a period of time such as one work shift, such density changes being attributable to a number of sources such as changes in the composition of the food being processed, changes in moisture content, and changes in the temperature of the food being processed. To complicate matters, such changes in density can occur gradually or can occur rather abruptly. For example, during the operation of a machine for forming products such as meat patties, the temperature of the ground meat within the supply hopper may gradually increase since such ground meat is normally stored at a relatively low temperature, (e.g., frozen) and processed at ambient room temperature. Thus, a gradual temperature change and associated density change can occur during the period in which a particular portion of the ground meat remains in the hopper. When the hopper of such a machine is reloaded with meat, the density change can be abrupt, since the food being loaded into the hopper will normally be at a lower temperature than that meat remaining in the hopper and may also exhibit a different density because of having originated from a different batch or lot of meat.
Secondly, manual control of forming pressure to control the weight of the formed product is extremely difficult since the machine operator cannot be aware that the formed products are not within a desired weight range until a number of products having an unacceptable weight have been produced. That is, since conventional food forming machines generally operate at a rather high rate of speed with a relatively large number of formed products being provided per unit time and passing from the machine on a conveyor or other transport mechanism, it is generally not possible to weigh one or more molded food products and adjust the forming pressure without producing a substantial number of underweight or overweight products.
Because of these problems it has become accepted practice within many areas of the food forming industry to simply rely on the experience and skill of the machine operator to produce as few unacceptable products as possible, reprocessing those products that do not meet the minimum weight requirement and delivering those products which exceed the weight requirement to the customer without extra charge. Such a practice is not entirely satisfactory since even the most skilled operator can produce a substantial number of formed products wherein the weight of the product deviates from the desired weight by a substantial amount.
Accordingly, it is an object of this invention to provide a method and apparatus for automatically controlling the density of a machine formed food product to thereby cause such a machine to produce formed food products of substantially uniform density and weight.
It is another object of this invention to provide an automatic control system for continuously controlling the forming pressure of a food forming machine such that the machine produces formed food products of a substantially uniform weight.
It is yet another object of this invention to provide an automatic control method and apparatus wherein the weight of a formed food product is controlled to supply products within a specified weight tolerance so that such products will be acceptable to the customers of the food processor while simultaneously decreasing the processing costs associated with prior art manual control means.